The ground state rotational spectrum of the fluorosulfate radical

The rotational spectra of the fluorosulfate (FSO3⋅) molecular radical in its vibronic ground state were measured in the millimeter-wave region and analyzed in detail using the matrix elements of the rotational, fine, and hyperfine Hamiltonian terms. The analysis of the assigned transition frequencies made it possible to derive very precise values of the rotational, centrifugal distortion and fine structure constants and to confirm the C3v molecular symmetry of the vibronic ground state unambiguously. In addition, an effective parameter of the “A1-A2 splitting” was determined. The rotational transitions of the FSO3⋅ free radical were observed, identified, and analyzed for the first time.